STRIGOLACTONE DERIVATIVES AS PLANT GROWTH REGULATOR COMPOUNDS

Abstract

Compounds of the formula (I) wherein the substituents are as defined in claim 1, useful as plant growth regulators and/or seed germination promoters.

##STR00001##

Claims

1. A compound of formula (I): ##STR00036## wherein Y is O, N—R.sup.4, S, S(O), or S(O).sub.2; n is 0 or 1; R.sup.1 and R.sup.2 are each independently selected from hydrogen and C.sub.1-C.sub.4alkyl; or R.sup.1 and R.sup.2 together with the carbon atom to which they are attached form a C.sub.3-C.sub.6cycloalkyl group; R.sup.3a, R.sup.3b, R.sup.3c, R.sup.3d are each independently selected from hydrogen, halogen, cyano, C.sub.1-C.sub.4alkyl, C.sub.1-C.sub.4haloalkyl, C.sub.1-C.sub.4alkoxy, C.sub.1-C.sub.4alkoxycarbonyl, C.sub.1-C.sub.4alkylcarbonyl, and C.sub.3-C.sub.6cycloalkyl, wherein each cycloalkyl moiety is optionally substituted with 1 to 3 groups represented by R.sup.5; R.sup.4 is hydrogen, C.sub.1-C.sub.4alkyl, formyl, C.sub.1-C.sub.4alkylcarbonyl, C.sub.1-C.sub.4alkoxycarbonyl, C.sub.1-C.sub.4haloalkylcarbonyl, C.sub.3-C.sub.8cycloalkylcarbonyl, phenyl, —S(O).sub.2—C.sub.1-C.sub.4alkyl, or —S(O).sub.2-phenyl; R.sup.5 is halogen, cyano, C.sub.1-C.sub.4alkyl, C.sub.1-C.sub.4haloalkyl, or C.sub.1-C.sub.4alkoxy; R.sup.6 is hydrogen or C.sub.1-C.sub.4alkyl; and X.sup.1 and X.sup.2 are each independently selected from hydrogen, halogen, cyano, C.sub.1-C.sub.4alkyl, and C.sub.1-C.sub.4alkoxy; or a salt or an N-oxide thereof.

2. The compound according to claim 1, wherein R.sup.1 and R.sup.2 are each independently selected from hydrogen and methyl.

3. The compound according to claim 1, wherein R.sup.3a, R.sup.3b, R.sup.3c, R.sup.3d are all hydrogen.

4. The compound according to claim 1, wherein R.sup.6 is hydrogen.

5. The compound according to claim 1, wherein R.sup.4 is —S(O).sub.2-C.sub.1-C.sub.4alkyl.

6. The compound according to claim 1, wherein R.sup.4 is —S(O).sub.2methyl.

7. The compound according to claim 1, wherein X.sup.1 and X.sup.2 are each independently selected from hydrogen, halogen, C.sub.1-C.sub.3alkyl, and C.sub.1-C.sub.3alkoxy.

8. The compound according to claim 1, wherein X.sup.1 is hydrogen or methyl.

9. The compound according to claim 1, wherein X.sup.2 is methyl.

10. The compound according to claim 1, wherein Y is O, S, or S(O).

11. A plant growth regulating or seed germination promoting composition, comprising the compound according to claim 1, and an agriculturally acceptable formulation adjuvant.

12. A method for regulating the growth of plants at a locus, said method comprising applying to the locus a compound according to claim 1.

13. A method for promoting the germination of seeds, comprising applying to the seeds, or a locus containing the seeds, the compound according to claim 1.

14. A method for improving the nutrient uptake of a crop, comprising applying to the plant or locus thereof, the compound according to claim 1.

15. Use of a compound of Formula (I) according to claim 1 for promoting the germination of seeds and/or for regulating plant growth.

16. A seed comprising a compound of Formula (I) according to claim 1.

17. The compound according to claim 2, wherein R.sup.3a, R.sup.3b, R.sup.3c, R.sup.3d are all hydrogen.

18. A method for regulating the growth of plants at a locus, said method comprising applying to the locus a compound according to a plant growth regulating amount of a composition according to claim 12.

19. A method for promoting the germination of seeds, comprising applying to the seeds, or a locus containing the seeds, the compound according to a seed germination promoting amount of a composition according to claim 13.

20. A method for improving the nutrient uptake of a crop, comprising applying to the plant or locus thereof, the compound according to a plant growth regulating or seed germination promoting composition according to claim 14.

21. Use of a compound of Formula (I) according to the composition as defined in claim 11, for promoting the germination of seeds and/or for regulating plant growth

22. A seed comprising a compound of Formula (I) according to a composition according to claim 11.

Description

EXAMPLES

[0193] The Examples which follow serve to illustrate the invention.

Compound Synthesis and Characterisation

[0194] The following abbreviations are used throughout this section: s=singlet; bs=broad singlet; d=doublet; dd=double doublet; dt=double triplet; bd=broad doublet; t=triplet; td=triplet doublet; bt=broad triplet; tt=triple triplet; q=quartet; m=multiplet; Me=methyl; Et=ethyl; Pr=propyl; Bu=butyl; DME=1,2-dimethoxyethane; THF=tetrahydrofuran; M.p.=melting point; RT=retention time, MH+=molecular cation (i.e. measured molecular weight).

[0195] Throughout this description, temperatures are given in degrees Celsius (° C.) and “m.p.” means melting point. LC/MS means Liquid Chromatography Mass Spectrometry and the description of the apparatus and the following HPLC-MS methods were used for the analysis of the compounds:

[0196] Method A: Spectra were recorded on a ZQ Mass Spectrometer from Waters (Single quadrupole mass spectrometer) equipped with an electrospray source (Polarity: positive or negative ions, Capillary: 3.00 kV, Cone: 30.00 V, Extractor: 2.00 V, Source Temperature: 100° C., Desolvation Temperature: 250° C., Cone Gas Flow: 50 L/Hr, Desolvation Gas Flow: 400 L/Hr, Mass range: 100 to 900 Da) and an Acquity UPLC from Waters (Solvent degasser, binary pump, heated column compartment and diode-array detector. Column: Waters UPLC HSS T3, 1.8 μm, 30×2.1 mm, Temp: 60° C., flow rate 0.85 mL/min; DAD Wavelength range (nm): 210 to 500) Solvent Gradient: A=H.sub.2O+5% MeOH+0.05% HCOOH, B=Acetonitrile+0.05% HCOOH) gradient: 0 min 10% B; 0-1.2 min 100% B; 1.2-1.50 min 100% B.

[0197] Method B: Spectra were recorded on a ZQ Mass Spectrometer from Waters (Single quadrupole mass spectrometer) equipped with an electrospray source (Polarity: positive or negative ions, Capillary: 3.00 kV, Cone: 30.00 V, Extractor: 2.00 V, Source Temperature: 100° C., Desolvation Temperature: 250° C., Cone Gas Flow: 50 L/Hr, Desolvation Gas Flow: 400 L/Hr, Mass range: 100 to 900 Da) and an Acquity UPLC from Waters (Solvent degasser, binary pump, heated column compartment and diode-array detector. Column: Waters UPLC HSS T3, 1.8 μm, 30×2.1 mm, Temp: 60° C., flow rate 0.85 mL/min; DAD Wavelength range (nm): 210 to 500) Solvent Gradient: A=H.sub.2O+5% MeOH+0.05% HCOOH, B=Acetonitrile+0.05% HCOOH) gradient: 0 min 10% B; 0-2.7 min 100% B; 2.7-3.0 min 100% B.

Example 1: this Example Illustrates the Preparation of 1,1-dichloro-3,8b-dihydro-2aH-cyclobuta[c]chromen-2-one (Compound IX-a)

[0198] ##STR00010##

[0199] To a flask under argon was added dry diethyl ether (21 mL), 2H-chromene (11.3 mmol, 1.5 g) and cuprouszinc (34.0 mmol, 4.4 g). To this suspension was added a solution of trichloroacetylchloride (22.7 mmol, 2.7 mL) and phosphorus oxychloride (17.0 mmol, 1.6 mL) in diethyl ether (15 mL). After complete addition, the suspension was heated at reflux for 16 hours. The reaction mixture was then filtered through a Celite® pad which was washed with diethyl ether. The filtrate was washed with water, saturated aqueous NaHCO.sub.3 solution and brine. The organic phase was then dried over sodium sulfate, filtered, concentrated under reduced pressure and the obtained crude residue was finally purify by column chromatography on silica gel affording compound of formula (IX-a) as a solid in 67% yield (7.6 mmol, 1.8 g). .sup.1H NMR (400 MHz, CDCl.sub.3) δ ppm 7.30-7.24 (m, 2H), 7.06 (m, 1H), 6.94 (m, 1H), 4.60 (dd, 1H), 4.32 (m, 1H), 4.23 (d, 1H), 3.87 (dd, 1H).

Example 2: this Example Illustrates the Preparation of 1,1-dichloro-3,3-dimethyl-2a,8b-dihydrocyclobuta[c]chromen-2-one (Compound IX-b)

[0200] ##STR00011##

[0201] To a flask under argon was added dry diethyl ether (21 mL), 2H-chromene (11.3 mmol, 1.5 g) and cuprouszinc (34.0 mmol, 4.4 g). To this suspension was added a solution of trichloroacetylchloride (22.7 mmol, 2.7 mL) and phosphorus oxychloride (17.0 mmol, 1.6 mL) in diethyl ether (15 mL). After complete addition, the suspension was heated at reflux for 16 hours. The reaction mixture was then filtered through a Celite® pad which was washed with diethyl ether. The filtrate was washed with water, saturated aqueous NaHCO.sub.3 solution and brine. The organic phase was then dried over sodium sulfate, filtered, concentrated under reduced pressure and the obtained crude residue was finally purify by column chromatography on silica gel affording compound of formula (IX-b) as a solid in 67% yield (7.6 mmol, 1.8 g). .sup.1H NMR (400 MHz, CDCl.sub.3) δ ppm 7.28-7.22 (m, 2H), 7.02 (m, 1H), 6.87 (m, 1H), 4.17 (d, 1H), 4.10 (d, 1H), 1.70 (s, 3H), 1.18 (s, 3H).

Example 3: this Example Illustrates the Preparation of 1,3a,4,9b-tetrahydrofuro[2,3-c]chromen-2-one (Compound IV-a)

[0202] ##STR00012##

[0203] Compound of formula (VI-a, 5.35 mmol, 1.3 g) was dissolved in a saturated solution of ammonium chloride (0.57 g) in methanol (36 mL). Cuprouszinc (1.03 g) was added and the resulting suspension was stirred at room temperature for 16 hours. The reaction mixture was then filtered through a Celite® pad which was washed with EtOAc. HCl aqueous solution (1M) was added to the organic solution, the phases separated and the organic layer was dried over Na.sub.2SO.sub.4, filtered and concentrated under reduced pressure to afford compound of formula (VIII-a) as an oil in quantitative yield (0.98 g). .sup.1H NMR (400 MHz, CDCl.sub.3) δ ppm 7.24-7.16 (m, 2H), 7.01 (td, 1H), 6.96 (m, 1H), 4.50 (m, 1H), 3.90-3.82 (m, 2H), 3.80-3.73 (m, 1H), 3.70-3.59 (m, 1H), 2.88 (m, 1H). Compound of formula (XI-a, 5.17 mmol, 0.9 g) was then dissolved in methanol (22 mL) and water (11.4 mL), magnesium monoperoxyphthalate (MMPP) was added in one portion and the reaction mixture was heated to 40° C. After 12 hours, the reaction was cooled to room temperature, quenched with a 10% aqueous Na.sub.2S.sub.2O.sub.3 and the organic phase washed with brine, dried over sodium sulfate and concentrated under reduced pressure affording compound of formula (IV-a) in 55% yield (0.74 g). .sup.1H NMR (400 MHz, CDCl.sub.3) δ ppm 7.18 (m, 1H), 7.10 (m, 1H), 7.00 (m, 1H), 6.91 (m, 1H), 4.93 (m, 1H), 4.37 (dd, 1H), 4.07 (dd, 1H), 3.84 (m, 1H), 3.15 (dd, 1H), 2.62 (dd, 1H).

Example 4: this Example Illustrates the Preparation of 4,4-dimethyl-3a,9b-dihydro-1H-furo[2,3-c]chromen-2-one (Compound IV-b)

[0204] ##STR00013##

[0205] Compound of formula (VI-a, 5.35 mmol, 1.3 g) was dissolved in a saturated solution of ammonium chloride (0.57 g) in methanol (36 mL). Cuprouszinc (1.03 g) was added and the resulting suspension was stirred at room temperature for 16 hours. The reaction mixture was then filtered through a Celite® which was washed with EtOAc. HCl aqueous solution (1M) was added to the organic solution, the phases separated and the organic layer was dried over Na.sub.2SO.sub.4, filtered and concentrated under reduced pressure to afford compound of formula (VIII-a) as an oil in quantitative yield (0.98 g). .sup.1H NMR (400 MHz, CDCl.sub.3) δ ppm 7.24-7.16 (m, 2H), 7.01 (td, 1H), 6.96 (m, 1H), 4.50 (m, 1H), 3.90-3.82 (m, 2H), 3.80-3.73 (m, 1H), 3.70-3.59 (m, 1H), 2.88 (m, 1H). Compound of formula (XI-a, 5.17 mmol, 0.9 g) was then dissolved in methanol (22 mL) and water (11.4 mL), MMPP was added in one portion and the reaction mixture was heated to 40° C. After 12 hours, the reaction was cooled to room temperature, quenched with a 10% aqueous Na.sub.2S.sub.2O.sub.3 and the organic phase washed with brine, dried over sodium sulfate and concentrated under reduced pressure affording compound of formula (IV-b) in 55% yield (0.74 g). .sup.1H NMR (400 MHz, CDCl.sub.3) δ ppm 7.16 (m 1H), 7.08 (m, 1H), 6.95 (m, 1H), 6.84 (m, 1H), 4.49 (d, 1H), 3.76 (m, 1H), 3.13 (dd, 1H), 2.70 (dd, 1H), 1.56 (s, 3H), 1.26 (s, 3H).

Example 5: this Example Illustrates the Preparation of 1,3,3a,8b-tetrahydrobenzofuro[2,3-b]pyrrol-2-one (Compound IV-c)

[0206] ##STR00014##

[0207] To a solution of compound (XII-c, 10.5 g, 51 mmol) and K.sub.2CO.sub.3 (2.0 eq, 102 mmol) in DMF (100 mL) was added at 0° C. 2-bromophenol (1.2 equiv., 61 mmol). The reaction was then heated under an argon atmosphere at 60° C. for 90 minutes. The reaction mixture was then partitioned between water and CH.sub.2Cl.sub.2 and the phases separated. The aqueous phase was extracted with a further portion of CH.sub.2Cl.sub.2 and the combined organic layers were washed with water, dried over magnesium sulphate and concentrated under vacuum. The resulting crude residue was purified by flash chromatography on SiO.sub.2 affording compound (XI-c) as a colorless oil that crystallized on standing in 92% yield (14.0 g). LCMS (Method A): RT 0.95 min; ES.sup.+ 300 (M+H.sup.+).

[0208] A solution compound (XI-c) (16.5 g, 3.35 mmol) in toluene (220 mL) was degassed with argon for 30 minutes, and vinyl stannane (1.3 equiv., 72 mmol) follow by Pd(PPh.sub.3).sub.4 (2.8 mmol, 99.8 mass %) were added. The resulting reaction mixture was heated to 100° C. and stirred for 16 hours. The reaction mixture was then cooled, concentrated under vacuum and purified by flash chromatography on SiO.sub.2 affording compound (X-c) as a colourless oil in 95% yield (12.9 g, 52.6 mmol). LCMS (Method A): RT 0.97 min; ES.sup.+ 247 (M+H.sup.+).

[0209] To a stirred solution of compound (X-c, 11 g, 44.8 mmol) in CH.sub.2Cl.sub.2 (179 mL) was added sequentially at room temperature 2-fluoropyridine (1.3 eq, 58.3 mmol, 5.1 mL) and Tf.sub.2O (1.2 eq, 53.8 mmol, 9.05 mL) dropwise and the resulting reaction mixture was stirred for 14 hours. Water (100 mL) was then added to the reaction and the biphasic mixture was stirred at room temperature for additional 16 hours. The reaction mixture was extracted with CH.sub.2Cl.sub.2, dried over sodium sulfate and concentrated under reduced pressure. Purification by flash chromatography on SiO.sub.2 afforded compound (VIII-c) in 77% yield (5.5 g, 34 mmol). .sup.1H NMR (400 MHz, CDCl.sub.3) δ ppm 7.32 (m, 1H), 7.22 (m, 1H), 6.98 (td, 1H), 6.91 (m, 1H), 5.75 (dt, 1H), 4.25 (td, 1H), 3.67 (ddd, 1H), 3.11 (dt, 1H).

[0210] To a solution of compound (VIII-c) (580 mg, 3.62 mmol) in AcOH (12 mL) at room temperature was added a 30% H.sub.2O.sub.2 solution (5 eq, 1.85 mL). The reaction was stirred for 16 hours at room temperature and then quenched with a saturated solution of NaHCO.sub.3 (100 mL) and EtOAc (100 mL). The organic layer was then dried over sodium sulfate and concentrated under vacuum. Purification by flash chromatography on SiO.sub.2 afforded compound (IV-c) as a colourless oil, which crystallized on standing in 80% yield (511 g, 2.90 mmol). LCMS (Method A): RT 0.70 min; ES.sup.+ 177 (M+H.sup.+).

[0211] Using a similar procedure to Example 5, the following compounds were prepared:

Compound (IV-d): 3a,8b-dihydro-1H-benzothiopheno[2,3-b]furan-2-one

[0212] ##STR00015##

[0213] LCMS (Method A): RT 0.77 min; ES.sup.+ 193 (M+H.sup.+).

Compound (IV-e): 4-methylsulfonyl-3a,8b-dihydro-1H-furo[2,3-b]indol-2-one

[0214] ##STR00016##

[0215] LCMS (Method A): RT 0.68 min; ES.sup.+ 254 (M+H.sup.+).

Example 6: this Example Illustrates the Preparation of (1Z)-1-(hydroxymethylene)-3a,8b-dihydrofuro[2,3-b]benzofuran-2-one (Compound II-c)

[0216] ##STR00017##

[0217] Compound of formula (IV-c) (5.7 mmol, 1.0 g) was suspended in dry toluene (or tert-butanol) and Bredereck's reagent (tert butoxybis(dimethylamino)methane) was then added (19.9 mmol, 3.5 g) under argon and the reaction mixture was stirred at room temperature for 2 hours. The reaction mixture was diluted with ethyl acetate (50 mL) and washed with water followed by brine, dried over Na.sub.2SO.sub.4 and the solvent evaporated under reduced pressure affording compound (V-c). Compound of formula (V-c) (5.2 mmol, 1.2 g) was then dissolved in 1,4-dioxane (10 mL) and aqueous hydrochloric acid solution (2M, 5.2 mL) and the resulting reaction mixture was stirred for 35 minutes at room temperature. Brine was added and extraction was done with ethyl acetate. The combined organic fractions were dried over sodium sulfate, the solvents evaporated and the resulting crude was used without further purification. Compound of formula (II-c) in 81% yield (4.5 mmol, 0.92 g). LCMS (Method A): RT 0.72 min; ES.sup.+ 203 (M−H.sup.+).

TABLE-US-00010 TABLE 2 LC/MS data (Rt = Retention time) for selected compounds of formula (II), which were prepared using the procedure of Example 6. Compound No. Name Structure LC/MS II-d 1-(hydroxy methylene)-3a,8b- dihydrobenzothiopheno [2,3-b]furan-2-one [00018] RT 0.78 min; ES.sup.− 219 (M − H.sup.+) II-e 1-(hydroxy methylene)-4- methylsulfonyl-3a,8b- dihydrofuro[2,3- b]indol-2-one [00019] RT 0.69 min; ES.sup.− 280 (M − H.sup.+) II-a 1-(hydroxy methylene)-4,9b- dihydro-3aH-furo[2,3- c]chromen-2-one [00020] RT 0.68 min; ES.sup.− 217 (M − H.sup.+) II-b 1-(hydroxy methylene)-4,4- dimethyl-3a,9b- dihydrofuro[2,3- c]chromen-2-one [00021] RT 0.84 min; ES.sup.− 245 (M − H.sup.+)

Example 7: This example illustrates the preparation of tert-butyl (1E)-1-[(4-methyl-5-oxo-2H-furan-2-yl)oxymethylene]-2-oxo-4,8b-dihydro-3aH-indeno[2,1-b]pyrrole-3-carboxylate (Compound I-1)

[0218] ##STR00022##

[0219] Compound of formula (II-c) (1.32 mmol) was dissolved in anhydrous 1,2-dimethoxyethane (4 mL), the resulting solution cooled to 0° C. and tBuOK (0.19 g, 1.72 mmol) was then added. After 10 minutes at 0° C., known compound of formula (A) (0.74 mmol) was added as a solution in DME (1 mL). The reaction mixture was then slowly warmed to room temperature. After 16 hours, a saturated aqueous NH.sub.4Cl solution was added and the reaction mixture was extracted with ethyl acetate. The combined organic extracts were washed with brine, dried over sodium sulfate and concentrated under vacuum.

[0220] The crude reaction residue was purified by flash chromatography on silica gel affording compound of formula (I-1) as a colorless foam and as a mixture of diastereoisomers in 72% yield (0.95 mmol). .sup.1H NMR (400 MHz, CDCl.sub.3) δ ppm (data given for the two diastereoisomers) 7.61 (d, 0.5H), 7.60 (d, 0.5 H), 7.21-7.33 (m, 2H), 7.06-7.09 (m, 0.5H), 7.03-7.06 (m, 0.5H), 6.96-7.01 (m, 1H), 6.91-6.96, (m, 1H), 6.54 (d, 0.5H), 6.53 (d, 0.5H), 6.27-6.31 (m, 1H), 4.85 (d, 1H), 2.09 (m, 3H).

Example 8: This example illustrates the preparation of (1E)-1-[(4-methyl-5-oxo-2H-furan-2-yl)oxymethylene]-4-oxo-3a,8b-dihydrobenzothiopheno[2,3-b]furan-2-one and (1E)-1-[(4-methyl-5-oxo-2H-furan-2-yl)oxymethylene]-4,4-dioxo-3a,8b-dihydrobenzothiopheno[2,3-b]furan-2-one (Compounds I-13 and I-19)

[0221] ##STR00023##

[0222] Compound of formula (I-7) (60 mg, 0.19 mmol) was dissolved in dichloromethane (2 mL), the resulting solution cooled to 0° C. and mCPBA (77 mass %, 0.042 g, 0.19 mmol) was then added. The reaction was stirred for 10 minutes at 0° C. Dichloromethane (10 mL) and a saturated aqueous NaHCO.sub.3 solution were successively added and the organic phase was washed with a saturated NaHCO.sub.3 aqueous solution. The organic phase was dried over sodium sulfate and concentrated under vacuum. The crude reaction residue was purified by flash chromatography on silica gel affording compound of formula (I-13) as a colorless foam. The product is obtained as a mixture of only 2 diastereoisomers in 75% yield (47 mg, 0.14 mmol). .sup.1H NMR (400 MHz, CDCl.sub.3) δ ppm (data given for the two diastereoisomers) 7.92-7.87 (m, 1H), 7.70-7.54 (m, 4H), 7.10-7.05 (m, 1H), 6.35 (br s, 0.5H), 6.32 (br s, 0.5H), 5.73 (two d, J=7.3 Hz, 1H), 5.51 (br d, J=5.9 Hz, 1H), 2.14-2.10 (m, 3H).

[0223] Using the same procedure, but with 2.5 equivalents of mCPBA (77 mass %, 105 mg, 0.48 mmol), compound of formula (I-19) was obtained as a colorless foam in 70% yield (46 mg, 0.13 mmol). .sup.1H NMR (400 MHz, CD.sub.3CN) δ ppm (data given for the two diastereoisomers) 7.83-7.60 (m, 5H), 7.17 (m, 0.5H), 7.14 (m, 0.5H), 6.42-6.40 (m, 0.5H), 6.40-6.38 (m, 0.5H), 5.73 (d, 0.5H), 5.72 (d, 0.5H), 5.17-5.15 (m, 0.5H), 5.15-5.14 (m, 0.5H), 2.01-1.99 (m, 3H).

TABLE-US-00011 TABLE 3 LC/MS data (R.sub.t = Retention time) for selected compounds of formula (I), which were prepared using the procedures of Example 7 or Example 8. Compound No. Name Structure LC/MS I-1 (1E)-1-[(4-methyl-5- oxo-2H-furan-2- yl)oxymethylene]- 3a,8b-dihydrofuro[2,3- b]benzofuran-2-one [00024] R.sub.t = 0.86 and 0.88 min; ES+ 301 (M + H.sup.+) I-2 (1E)-1-[(3,4-dimethyl- 5-oxo-2H-furan-2- yl)oxymethylene]- 3a,8b-dihydrofuro[2,3- b]benzofuran-2-one [00025] R.sub.t = 0.90 and 0.91 min; ES+ 315 (M + H.sup.+) I-7 (1E)-1-[(4-methyl-5- oxo-2H-furan-2- yl)oxymethylene]- 3a,8b- dihydrobenzothiopheno [2,3-b]furan-2-one [00026] R.sub.t = 0.90 and 0.92 min; ES+ 317 (M + H.sup.+) I-8 (1E)-1-[(3,4-dimethyl- 5-oxo-2H-furan-2- yl)oxymethylene]- 3a,8b- dihydrobenzothiopheno [2,3-b]furan-2-one [00027] R.sub.t = 0.94 and 0.96 min; ES+ 331 (M + H.sup.+) I-13 (1E)-1-[(4-methyl-5- oxo-2H-furan-2- yl)oxymethylene]-4- oxo-3a,8b- dihydrobenzothiopheno [2,3-b]furan-2-one [00028] R.sub.t = 0.71 min; ES+ 333 (M + H.sup.+) I-14 (1E)-1-[(3,4-dimethyl- 5-oxo-2H-furan-2- yl)oxymethylene]- 3a,8b-dihydrofuro[2,3- b]benzofuran-2-one [00029] R.sub.t = 0.73 min; ES+ 347 (M + H.sup.+) I-19 (1E)-1-[(4-methyl-5- oxo-2H-furan-2- yl)oxymethylene]-4,4- dioxo-3a,8b- dihydrobenzothiopheno [2,3-b]furan-2-one [00030] R.sub.t = 0.71 min; ES+ 349 (M + H.sup.+) I-20 (1E)-1-[(3,4-dimethyl- 5-oxo-2H-furan-2- yl)oxymethylene]-4,4- dioxo-3a,8b- dihydrobenzothiopheno [2,3-b]furan-2-one [00031] R.sub.t = 0.78 min; ES+ 363 (M + H.sup.+) I-25 (1E)-1-[(4-methyl-5- oxo-2H-furan-2- yl)oxymethylene]-4- methylsulfonyl-3a,8b- dihydrofuro[2,3- b]indol-2-one [00032] R.sub.t = 0.84 min; ES+ 378 (M + H.sup.+) I-26 (1E)-1-[(3,4-dimethyl- 5-oxo-2H-furan-2- yl)oxymethylene]-4- methylsulfonyl-3a,8b- dihydrofuro[2,3- b]indol-2-one [00033] R.sub.t = 0.87 min; ES+ 392 (M + H.sup.+) I-31 (1E)-1-[(4-methyl-5- oxo-2H-furan-2- yl)oxymethylene]- 4,9b-dihydro-3aH- furo[2,3-c]chromen-2- one [00034] R.sub.t = 0.82 min (A); MS: m/z = 315 (M + 1) I-37 (1E)-4,4-dimethyl-1- [(4-methyl-5-oxo-2H- furan-2- yl)oxymethylene]- 3a,9b-dihydrofuro[2,3- c]chromen-2-one [00035] R.sub.t = 0.95 min (A); MS: m/z = 343 (M + 1)

Biological Examples

Example B1: Dark Induced Senescence of Corn Leaf

[0224] It is known that strigolactones regulate (accelerate) leaf senescence, potentially through D14 receptor signaling.

[0225] Corn plants of variety Multitop were grown in a greenhouse with relative 75% humidity and at 23-25° C. for 6 weeks. 1.4 cm diameter leaf discs were placed into 24-well plates containing test compounds in a concentration gradient (100 μM-0.0001 μM) at a final concentration of 0.5% DMSO. Each concentration was tested in 12 replicates. Plates were sealed with seal foil. The foil was pierced to provide gas exchange in each well. The plates were placed into the completely dark climatic chamber. Plates were incubated in the chamber with 75% humidity and at 23° C. for 8 days. On days 0, 5, 6, 7 and 8 photographs were taken of each plate, and image analysis conducted with a macro developed using the ImageJ software. The image analysis was used to determine the concentration at which 50% senescence was achieved (IC50), see Table 4. The lower the value, the higher senescence induction potency.

TABLE-US-00012 TABLE 4 IC50 of compounds (I) for dark induced senescence of corn leaf Compound IC50 (μM) I-1  0.03 I-2  0.015 I-8  0.04  I-13  0.015  I-31  0.03